Is it just me or are people fucking thick?

Mir Nyet · Post by **Mir Nyet** » Tue Dec 12, 2006 3:48 pm 0

Lossing the plot slightly here

Ok, we have a rolling road that moves at a speed which is enough to push enough force into the plane to negate the thrust of the engines, will force the plane to remain stationary (which is the original point) then the plane will not lift. Regardless of the method used, if the force of the engines is being negated, then we have a stationary plane.

The original riddle was all about does a plane fly because of the thrust from the engines alone - which is no, a plane flies because of the areas of lower pressure across its upper surfaces. As I mentioned before, if there is no air passing over the planes surfaces to be accelerated, thus causing areas of lower pressure, then then plane does not fly regardless of the thrust from the engine.

zip accident · Post by **zip accident** » Tue Dec 12, 2006 3:51 pm 0

tufty wrote:

match the speed of the wheels

I guess I went off on one, that works if you take the speed of the wheels from the centre of the axle, the paradox I noticed arises if you take the speed of the wheel at the point of contact between the tire and the treadmill.

Mir Nyet · Post by **Mir Nyet** » Tue Dec 12, 2006 3:53 pm 0

zip accident wrote:
Mir Nyet wrote:

How can the plane take off if it is effectively standing still?
The example you gave was in a wind tunnel. In that case, the roadspeed is 200, the groundspeed is 0, the airspeed is 200, so the plane will fly, since airspeed is what matters.

In a wind tunnel, the air is being pushed over the car to simulate the car moving, in the real world (i.e. outside of a wind tunnel) the plane pushes itself through the air to force the air over its surfaces to generate lower pressure areas gaining lift. If the plane is stationary, then this never happens...

The rolling road is not there to match the rotational speed of the wheels, it is there to provide a retardational force to the entire plane via the planes landing gear that matches the output of the planes engine, the speed of the road would be calculated on the actually motion of the plane, not its wheels, the wheels are purely the method in which this retardation is applied to the plane. You could adjudge motion in the plane via the speed of its wheels, but you would not tie the motion of the rolling road to anything other than the overal motion of the plane.

Regardless of how we force the plane to remain stationary negating the force of its engines, if the plane is physically stationary, it cannot lift due to the lack of air passing over its surfaces.

Stone · Post by **Stone** » Tue Dec 12, 2006 4:02 pm 0

Is Jedburgh going to come back, or not?

Now, if you put the magical treadmill in the vacuum...

Stone

tufty · Post by **tufty** » Tue Dec 12, 2006 4:05 pm 0

Mir Nyet wrote:Regardless of how we force the plane to remain stationary negating the force of its engines, if the plane is physically stationary, it cannot lift due to the lack of air passing over its surfaces.

*if* you can force the plane to remain stationary.

Even if you rotate the wheels fast enough to liquify the bearings, you will never induce enough force simply by causing the wheels to rotate to overcome the propulsive force applied by the motor. But according to the rules, you're only allowed to rotate them twice as fast as they would normally rotate. You lose in both cases.

Simon

zip accident · Post by **zip accident** » Tue Dec 12, 2006 4:07 pm 0

Mir Nyet wrote:

Ok, we have a rolling road that moves at a speed which is enough to push enough force into the plane to negate the thrust of the engines, will force the plane to remain stationary (which is the original point) then the plane will not lift.

True enough, except that that wasn't the original question.

wrote:

Regardless of how we force the plane to remain stationary negating the force of its engines,

No, how we stop the plane is entirely relevant, if for instance it's a headwind, then it can take off.

if the plane is physically stationary,

It's all relative. If the plane is stationary relative to the air, it can't take off. If it's stationary relative to the ground, then it depends what the air is doing whether the plane can take off or not. I believe physicists call this "frames of reference".

Stone wrote:

Star Smashers of the Glaxay Rangers

http://www.amazon.co.uk/Smashers-Galaxy ... 1932100830

Mir Nyet · Post by **Mir Nyet** » Tue Dec 12, 2006 4:09 pm 0

tufty wrote:
Mir Nyet wrote:Regardless of how we force the plane to remain stationary negating the force of its engines, if the plane is physically stationary, it cannot lift due to the lack of air passing over its surfaces.
*if* you can force the plane to remain stationary.

Even if you rotate the wheels fast enough to liquify the bearings, you will never induce enough force simply by causing the wheels to rotate to overcome the propulsive force applied by the motor. But according to the rules, you're only allowed to rotate them twice as fast as they would normally rotate. You lose in both cases.

Simon

But if the plane was stationary - which was the conditon in the riddle, then regardless of the thrust of the engine, it simply would not fly...

We can twist this as many ways as we like, and argue fine detail, but

You cannot change the laws of physics... No airflow, no lift.

Alarm · Post by **Alarm** » Tue Dec 12, 2006 4:11 pm 0

Eight pages so far about this stupid question?

Your all fick. Nnnnngh.

kalmar · Post by **kalmar** » Tue Dec 12, 2006 4:12 pm 0

Mir Nyet wrote:But if the plane was stationary - which was the conditon in the riddle

No, it wasn't.

Space Cowboy · Post by **Space Cowboy** » Tue Dec 12, 2006 4:13 pm 0

Mir Nyet wrote:We can twist this as many ways as we like, and argue fine detail, but You cannot change the laws of physics... No airflow, no lift.

What else needs to be said?

Mir Nyet · Post by **Mir Nyet** » Tue Dec 12, 2006 4:18 pm 0

kalmar wrote:
Mir Nyet wrote:But if the plane was stationary - which was the conditon in the riddle
No, it wasn't.

Err

"In brief, an aeroplane is put on a magical conveyor belt that automatically matches the plane's speed and keeps it stationary. The question is, can the aeroplane take off?"

Yes it was

kalmar · Post by **kalmar** » Tue Dec 12, 2006 4:23 pm 0

Mir Nyet wrote:
kalmar wrote:
Mir Nyet wrote:But if the plane was stationary - which was the conditon in the riddle
No, it wasn't.

Err

"In brief, an aeroplane is put on a magical conveyor belt that automatically matches the plane's speed and keeps it stationary. The question is, can the aeroplane take off?"

Yes it was

Not what the article said. As pointed out, the version Jedburgh posted is impossible anyway. But yes, it's obvious that if you stop an aircraft from moving, it won't take off. Why bother arguing the point though?

juice · Post by **juice** » Tue Dec 12, 2006 4:23 pm 0

There's a nice response here, with an easy-to-copy example:

http://txfx.net/2005/12/08/airplane-on-a-conveyor-belt/

I think the main issue is with the wording of the question (and assumptions about airplane wheels)...

kalmar · Post by **kalmar** » Tue Dec 12, 2006 4:25 pm 0

juice wrote:There's a nice response here, with an easy-to-copy example:

http://txfx.net/2005/12/08/airplane-on-a-conveyor-belt/

I think the main issue is with the wording of the question (and assumptions about airplane wheels)...

Heh, the summary of that is "Gahâ€¦ people are freakinâ€™ stupid.".
I think we've covered all those points too.

Mir Nyet · Post by **Mir Nyet** » Tue Dec 12, 2006 4:30 pm 0

kalmar wrote:
juice wrote:There's a nice response here, with an easy-to-copy example:

http://txfx.net/2005/12/08/airplane-on-a-conveyor-belt/

I think the main issue is with the wording of the question (and assumptions about airplane wheels)...
Heh, the summary of that is "Gahâ€¦ people are freakinâ€™ stupid.".
I think we've covered all those points too.

It is amusing to play with these things however, and explore our own assumptions about how things work. Don't know about anyone else, but I found this thread quite fun.